合并多个 Excel 文件

• 添加依赖

<dependency>
	<groupId>org.apache.poi</groupId>
	<artifactId>poi-ooxml</artifactId>
</dependency>
<dependency>
	<groupId>cn.hutool</groupId>
	<artifactId>hutool-core</artifactId>
</dependency>

• 工具类

package net.saisimon.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;

import org.apache.poi.hssf.usermodel.HSSFWorkbook;
import org.apache.poi.ss.usermodel.Cell;
import org.apache.poi.ss.usermodel.Row;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.xssf.streaming.SXSSFWorkbook;
import org.apache.poi.xssf.usermodel.XSSFWorkbook;

public class Utils {
	
	private static final int XLS_MAX_ROWS = 65535;
	private static final int XLSX_MAX_ROWS = 1048575;
	
	/**
	 * 合并多个 Excel 文件
	 * 
	 * @param mergedFile 合并后的文件
	 * @param files      待合并的文件
	 * @param isXlsx     合并文件类型是否是 xlsx
	 * @throws IOException       合并异常
	 */
	public static void mergeExcel(File mergedFile, List<File> files, boolean isXlsx) throws IOException {
		if (mergedFile == null || files == null) {
			return;
		}
		try (Workbook mergedWorkbook = isXlsx ? new SXSSFWorkbook() : new HSSFWorkbook();
				FileOutputStream out = new FileOutputStream(mergedFile)) {
			Sheet newSheet = mergedWorkbook.createSheet();
			int start = 0;
			for (File file : files) {
				if (file == null) {
					continue;
				}
				try (Workbook oldWorkbook = isXlsx ? new XSSFWorkbook(new FileInputStream(file)) : new HSSFWorkbook(new FileInputStream(file))) {
					int oldSheetSize = oldWorkbook.getNumberOfSheets();
					for (int i = 0; i < oldSheetSize; i++) {
						Sheet oldSheet = oldWorkbook.getSheetAt(i);
						int oldRowSize = oldSheet.getLastRowNum();
						for (int j = 0; j <= oldRowSize; j++) {
							if (start == (isXlsx ? XLSX_MAX_ROWS : XLS_MAX_ROWS)) {
								newSheet = mergedWorkbook.createSheet();
								start = newSheet.getLastRowNum();
							}
							Row oldRow = oldSheet.getRow(j);
							Row newRow = newSheet.createRow(start);
							copyRow(oldRow, newRow);
							start++;
						}
					}
				}
			}
			mergedWorkbook.write(out);
		}
	}

	private static void copyRow(Row oldRow, Row newRow) {
		newRow.setHeight(oldRow.getHeight());
		for (int i = oldRow.getFirstCellNum(); i <= oldRow.getLastCellNum(); i++) {
			Cell oldCell = oldRow.getCell(i);
			if (null != oldCell) {
				copyCell(oldCell, newRow.createCell(i));
			}
		}
	}
	
	private static void copyCell(Cell oldCell, Cell newCell) {
		switch (oldCell.getCellTypeEnum()) {
			case FORMULA:
				newCell.setCellFormula(oldCell.getCellFormula());
				break;
			case NUMERIC:
				if (org.apache.poi.ss.usermodel.DateUtil.isCellDateFormatted(oldCell)) {
					newCell.setCellValue(cn.hutool.core.date.DateUtil.formatDate(oldCell.getDateCellValue()));
				} else {
					newCell.setCellValue(oldCell.getNumericCellValue());
				}
				break;
			case BLANK:
				newCell.setCellValue(oldCell.getStringCellValue());
				break;
			case BOOLEAN:
				newCell.setCellValue(oldCell.getBooleanCellValue());
				break;
			case STRING:
				newCell.setCellValue(oldCell.getStringCellValue());
				break;
			default:
				break;
		}
	}
	
}